The present invention relates to a method and device for discriminating the type of a disk loaded in an optical disk apparatus and, more particularly, to a method and device for discriminating the type of a disk in which a transparent substrate is formed on a reflecting layer.
In recent years, along with the diversification of the CD-ROM format and the advent of DVDs, various types of optical disks have been introduced and will be developed and introduced in the future. For example, among normal CDs, there are music CDs, and among CD-ROM formats, there are read-only CD-ROMs, writable CDRs, CDR2s that can be read even with different wavelengths, erasable CD-Es, and the like. Among DVDs, there are one-layer disks, two-layer disks, writable DVD-Rs, and writable/readable DVD-Rs. A DVD disk apparatus for these DVDs must be able to play back not only DVDs but also CDs.
Various proposals have been made concerning a disk apparatus that can play back not only DVDs but also CDs, and such a disk apparatus is under development. In the development of such a disk apparatus, it is requested that the type of a loaded disk be discriminated within a short period of time and that the respective portions of the apparatus be set according to the disk type.
According to an example of a disk discrimination method, i.e., a disk recognition method, a disk is played back under an assumption that the playback target is a one-layer DVD. If data cannot be loaded, then this disk is played back under an assumption that it is a CD. According to this method, in a worst case, data read can only be made through four assumption steps, i.e., the disk is not a one-layer DVD, the disk is not a two-layer DVD, the disk is not a normal CD, and the disk is not a normal CD but is a CD having a lower reflectance than that of a normal CD. According to this disk recognition method, in a fortunate case, data read can be made through one step. However, in a worst case, data read can only be made through four steps. On the user side, this means that a time required after the disk is set in the apparatus until the apparatus recognizes the disk, that is, the total time of initializing time and ready time is not always constant but becomes long or short. Accordingly, the user will fear or suspect that the apparatus be broken, leading to a conclusion that the apparatus is not easy to use.